Business groups claim their members could be targeted by union "thuggery" and boycotts if they help the federal government defend last week's decision by the Fair Work Commission to pare back penalty rates for Sundays and public holidays.

In a sign of emerging tensions between the business community and the Turnbull government, Employment Minister Michaelia Cash rang the heads of key business groups on Monday night seeking their help fighting a campaign by Labor and the unions against the decision which affects 680,000 workers in retail, pharmacy, hospitality and fast-food.

With Labor and the unions gearing up for a repeat of the anti-WorkChoices, Your Rights at Work campaign of a decade ago, the government is dismayed that some business groups, many of which have spent years advocating industrial relations reform, including penalty rate changes, are not prepared to get their hands dirty now.

The groups were supposed to meet last night to discuss the situation but it was cancelled for scheduling reasons.

Those called by Senator Cash included Business Council of Australia chief executive Jennifer Westacott, Australian Chamber of Commerce chief executive James Pearson and the Australian Industry Group's Innes Willox.

But the BCA argued its members, the nation's 127 largest businesses, were not directly affected by the decision and therefore it was not the BCA's fight.

One government source said the penalty rates decision could help a small business become a big business so the BCA should get involved.

"Everyone has a role to play," he said.

Mr Willox said his organisation had argued before the Fair Work Commission for two years to reduce penalty rates "for our fast food industry members" and would continue to promote the decision.

But he said businesses risked recrimination if they campaigned.

"The decision will be phased in over at least two years. Our members and the business community generally are very pleased with the decision but individual business are understandably reluctant to speak up knowing the risk of union intimidation, thuggery, boycotts or protests," he said.

"We have not stopped talking about the issue for more than two years and Ai Group was in the commission arguing the case for fairer penalty rates while other business groups were not.

"I talk to the minister and opposition regularly. We continue to press the penalty rates case publicly and privately to help ensure the commission's sensible and balanced decision is upheld and have taken this position consistency for years."

Mr Pearson released a statement against reiterating his support for the decision.

"While some staff may have their hourly pay reduced, extra work hours are likely to be available, and people who up until now have been squeezed out of the job market will get new opportunities," he said.

"We know that retail and hospitality are the sectors where many young people get their first job, so this decision will be a boon for youth employment."

The Fair Work Commission decision pared back rates in just four of 122 awards but 680,000 people will suffer a loss of take-home pay. Labor is promising to reverse the decision if elected.

Labor leader Bill Shorten told a meeting of his caucus on Tuesday "this was a fight Labor was born for".